Hello, im building a keyboard with 62 buttons. Each button has to be wired to an input on a shift register(74hc165).
Im using lots of very thin enamelled copper wire taken from an old speaker coil to solder to make connection between button pin to register input. Its likely that quite a few enamelled wire connections will cross over each over(enamelled so no shorts!)
Will there be too much interference in my keyboard leading to false button presses?
Does it make a difference whether i pull registers inputa to high or low in terms of interference?
Will my wire cause button presses not to be registered, e.g voltage losses. The longest wire i have is 30cm to reach buttons at the end of the keyboard
My enameled copper speaker coil wire is about as thin as a human hair
Assuming you are using pull-up resistors, lower resistance is more immune to noise/interference. I'd try starting with 10K and go-down if you have problems.
The only trade-off is current. i.e. If you pull-down a 10K resistor from 5V, that's 0.5mA. A 1K resistor takes 5mA. With switches/buttons a few mA is not a problem. (Unless maybe if you press all of the buttons at once. )
At the moment, i have 100 10k resistors at hand, which i plan to use to pull up the register inputs
Yes, it is a bit odd that im wiring each button to an input, but i had a lot of registers and resistors hanging around, didn’t have many diodes so decided to avoid a matrix, makes the code a little more simple too.
Thanks for all the replies, my enamel is still very new. So far ive been putting a layer of tape between wires that by chance cross each over. Is this necessary? If it doesn’t make a difference to interference then i would prefer not too
There are no "signals" in your design, so where could interference come from? There is only DC voltage changes and only when a key is pressed. Have you checked for the "interference" with an oscilloscope and where did you check? Do not try to create problems for yourself.
Buttons have ground running into their inputs
Buttons outputs are pulled up to 3.3v until the button is pressed where its output drops to ground, registering as a press. With all the 3.3v lines that sit close to buttons output wires, i worry it could effect the buttons outputs lines enough that presses might not register
I would not worry about the 3.3V lines. If those are noisy, the Arduino won't work.
AC noise from nearby motors, overhead fluorescent lights, nearby household AC wiring etc. are the most common source of interference, and long single wire leads are great antennas for picking that up.
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